You make a great point and I'm sorry about that. To answer some of your questions and try to add more detail:

Strings are UTF-8. Internally Parquet has the concept of "physical types" (ie how bytes are arranged) and "logical types". 64 bit ints are just physical with no logical type. DateTimes are 64 bit int physical types (millis since unix epoch - aka "Javascript time") with a logical type of "datetime" so you know to read it that way.

Bool columns are bits in a row.

The "data bearing" parts of a file can be compressed and usually are. Most are using snappy, a fastish, moderate compression codec. I believe some are also using zstd. One of the common questions people ask is: "how does it compare against .csv.gz" and the answer is favourably. Gzipped csv is even slower to read and write and usually about 30% bigger on disk.